The current noninvasive method of defining finger joint deformity relies on a biplanar roentgenographic technique. This method determines accurate joint orientation deformity in three dimensions, as well as any associated joint subluxation or dislocation. Change of tendon location due to disease will be observed during surgery and simulated on the computerized analytical model of the hand. Well-defined pathology of the hand will be studied so that their exact anatomical deformities can be standardized. These abnormal patients will be evaluated functionally using the instruments developed in this study. A complete disability profile for each type of pathology can then be described. This data combined with the anatomical change in the joints and tendons can provide the needed information for the calculation of abnormal forces in the hand during isometric functions. Currently, three types of deformity have been studied. These include trauma to joint and tendon, flexor tendon subluxation, and joint deformity due to arthritic disease. An analysis of specific examples provides an explanation for the cause of deformity, and it may also suggest a proper method of correction. Using these data as a basis, theoretical analysis can be performed on the currently available methods of treatment to examine their effectiveness in correcting deformities and functional recovery. Patients with rheumatoid or osteo-arthritic hands who are candidates for total joint replacement are examined in the laboratory both pre and postoperatively. Their pathological deformity and functional deficits before surgical reconstruction are quantitated so that the postoperative results can be compared prospectively to assess the effect of surgery. This evaluation regime can also be used to compare different finger joint prostheses and to study the subsequent postoperative rehabilitation programs for patients after major hand reconstruction. BIBLIOGRAPHIC REFERENCES: Cooney, W.P., Chao, E.Y.: Biomechanical analysis of static forces in the thumb during hand functions. J. Bone Joint Surg. 59A:27-36 (January) 1977. Chao, E.Y., An, K.N.: Graphical interpretation of the solution to the redundant problem in biomechanics. ASME Paper No. 77-BIO-1 (June) 1977.